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Monday, June 11, 2007

Is the US currently suffering from global warming droughts?

Britain's Independent has a story proclaiming “The wrath of 2007: America’s great drought”. It argues that : “America is facing its worst summer drought since the Dust Bowl years of the Great Depression. Or perhaps worse still.” Bad news sells.

You get into the story and it says the main impact of this “great drought” is “restrictions on hose pipes and garden sprinklers in eastern cities.” I don’t remember a summer when that didn’t happen for some of the time. As usual the report has a couple of quotes from the “climate-change-is-happening-now” crowd. As usual no one who disputes that is quoted.

Perhaps the worst section was the closing paragraph which describes the Dust Bowl of the 1930s. “When drought hit, the soil dried, became dust, and blew eastwards, mostly in large black clouds. This caused an exodus from Texas, Arkansas, Oklahoma, and the surrounding Great Plains, with more than half a million Americans left homeless in the Great Depression.” Now it is unclear what he is saying but it appears to suggest, or can be interpreted as saying, that the drought of the 1930s caused the Great Depression. Of course the Depression came first.

The major potential problem for the US from any temporary drought is to crops. So I looked at the Crop Moisture Index of the National Oceanic & Atmospheric Administration. You will see it below. The first thing that strikes me about it is that the vast majority of the United States is in the normal to moist range. This is especially true of the major food production areas.

When I last blogged on Gore’s claims about drought I noted that the Southeast had dry conditions mainly in Georgia and the Carolinas. If you now look at the index here you will see that the Carolinas are all recovered and back to normal and that the dry conditions moved westward. Half of Georgia is back to normal. It is now mainly Alabama that is dryer than normal. The last week saw heavy rainfall across both Florida and Georgia. The Tampa Bay area got 7 inches of rain with most the region getting 3 to 6 inches. More moderate rainfall came to the Carolinas as well.

Again the one region that remains very dry is the one region that remains very dry almost every year. California, Nevada, Arizona and Utah are, and always have been, very dry states. Southern California has always relied on water imports. And Arizona is famously dry and warm, that is one reason people move there. But even there the monsoon season is about to hit as it normally does.

Crop moisture is one thing and rain is another. So what do we find when it comes to rain? Here is the Standard Precipitation Index for the last 9 months, until the end of May. Again the vast majority of the United States is normal. And more areas have more rain than normal than have less rain than normal. You see Georgia, Florida and Alabama are drier than normal, something last weeks storms mitigated, as are California, Oregon and Nevada. Arizona, that was prominently mentioned as being abnormally dry in the Independent is actually shown as having had normal rainfall over the last 9 months. But normal in Arizona is still relatively dry.

The claim made by the Church of Anthropogenic Warming is that drought conditions are getting worse as rainfall declines due to climate change. And the Independent makes this claims specifically for the summer season. Yet as this chart shows the rainfall trends in the United States, over the summer season, has been toward increased rainfall. You can see that from 1900 to 1910 rainfall was above average, In the 1930s it was below average. But for the 1990s, the decade of “warming”, we see above normal rainfall which continues right up to the end of this chart in 2006.

And if we look a historic charts regarding drought in the United States we don’t see this increased drought. Here is the chart of which areas were dry in the early 1990s.

The 1990s were much better than the late 70s as this chart shows.

On the other hand the mid 1950s were very bad. Remember this is before the major “impact of global warming”.

The 1930s were not particularly good either. Again this is prior to supposed man-made warming.

What is actually interesting is that the historic maps of drought areas show wide variability. In the early 1900s it was mainly Arizona and Utah that had drought. The next decade showed drought mainly in Texas In the 1920s drought was mainly in Nevada. In the 1930s it was mainly Oklahoma, Colorado, Idaho, Montana and the Dakotas. In the 40s there was little to no drought anywhere. For the early 1950s there was massive drought covering about half the continental US but by the late 1950s most of it had cleared. The 1960s saw most of the US spending less than 20% of the time in drought conditions. And the 1970s were much improved over that. The 1980s were moderate in terms of drought with the regions hit mainly the Pacific Northwest and the northern Plain states.

The Independent makes much to do about Lake Okeechobee in Florida being relatively dry. But they ignore the reality of the lake. It is not a lake in the traditional sense of the word. It is large, second only to Lake Michigan in size but it is extremely shallow, averaging only 9 feet in depth. Much of it is only 1 foot deep and at the deepest it is the depth of most built-in swimming pools. It is encompassed by a 20 foot dike that was built in the 1930s. So it is a very shallow lake.

The Independent reported: “Nothing, though, was so strange as the fires that broke out over about 12,000 acres on the northern edge of the lake at the end of May.” Considering that entire sections of the lake are normally just one foot deep one would expect sections to dry out completely, during a dry spell, making a possible fire not particularly strange at all. However, the lake is drier than normal. But if the Church of AGW are correct this shouldn’t be the case.

Lake Okeechobee relies heavily on storms hitting the Florida coast. The Church of AGW, Archbishop Al Gore in particular, have been claiming that warming will increase the number and severity of hurricanes hitting the United States thus bringing more rainfall to Florida not less. But last year not a single hurricane hit the United States. So that means that Florida didn’t get the rainfall it normally would and that means Lake Okeechobee would be drier than normal.

This damned-if-you do, damned-if-you-don’t attitude is what irks me about this global warming religion. Lake Okeechobee is drier than normal due, in large part, to the absence of hurricanes last year. But they tell us it is drier due to global warming and long term climate change. At the same time they argue that increased hurricanes are a result of man-made warming. So if the lake is full, due to hurricanes, they are right. And if the lake is lower than normal, because of few or no hurricanes, they are right. They have their bets hedged in such a way that anything that happens seems to prove man-made warming. Personally I get the impression that anything that happens is considered proof of man-made warming.